Characterization of the ZO-1 protein in endothelial and other cell lines.
A high molecular weight tight junction-associated protein, ZO-1, has been demonstrated in liver (hepatocytes) and in both epithelium and endothelium. We carried out studies to examine the presence of the protein in vascular endothelial cell cultures and several other types of cultured cells, and the relationship between the ZO-1 protein content and confluency of endothelial cell monolayers. Immunofluorescence labelling of endothelial monolayers and two types of epithelial monolayers, IEC-6 and MDCK, with monoclonal antibody against ZO-1 protein localized the protein to the cell peripheries. Its association with the cell periphery only occurred when cells had contact with one another as demonstrated in endothelial cells. We have been able to show a positive correlation between the ZO-1 content of the cells and the extent of monolayer confluency in the endothelial cells by immunoblotting. The protein is much less expressed in nonconfluent endothelial cell monolayers and totally absent from mouse myeloma cultures. The presence and confluence-related expression of the protein in endothelium give support to the hypothesis that tight junctions exist in confluent endothelial cells and that the ZO-1 protein is expressed under the conditions where tight junction interactions occur.
Li
C X
CX
Department of Physiology, University of Alberta, Edmonton, Canada.
Poznansky
M J
MJ
D000818:Animals; D002417:Cattle; D002450:Cell Communication / Q000502:physiology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000737:chemistry*; D004848:Epithelium / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D007365:Intercellular Junctions / Q000737:chemistry; D007413:Intestinal Mucosa / Q000737:chemistry; D007684:Kidney Tubules / Q000737:chemistry; D008565:Membrane Proteins / Q000032:analysis*; D010750:Phosphoproteins / Q000032:analysis*; D062826:Zonula Occludens-1 Protein
D008565:Membrane Proteins; D010750:Phosphoproteins; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein